Controller for a resonant power converter

1. A method of controlling a resonant power converter, comprising: comparing an output voltage or current of the converter to at least one reference voltage or current; and operating one or more primary side switches of the resonant power converter by: (i) enabling primary side switching signals based on a first selected result of the comparison; and (ii) disabling primary side switching signals based on a second selected result of the comparison; wherein a primary side switching signal for each primary side switch includes at least one off-on-off transition; wherein the operating one or more primary side switches of the resonant power converter by enabling and disabling primary side switching signals regulates the output voltage or current.

2. The method of claim 1 , wherein the primary side switching signals for a pair of primary side switches are edge-synchronous, opposite polarity, and have 50% duty cycle.

3. The method of claim 1 , including deriving a frequency of the primary side switching signals from a clock frequency.

4. The method of claim 3 , wherein an on period of the primary side switching signals is an integer multiple of a clock period and is synchronized with the clock frequency.

5. The method of claim 3 , including using a counter to derive the switching frequency from the clock frequency.

6. The method of claim 5 , wherein the counter begins counting at a next clock edge upon receiving the first selected result of the comparison.

7. The method of claim 6 , wherein the next clock edge is positive.

8. The method of claim 1 , wherein the first selected result of the comparison is when the converter output voltage or current falls below at least one reference voltage or current.

9. The method of claim 3 , wherein the clock frequency is a multiple of the switching frequency and the primary side switching signals are enabled with a delay of less than one switching cycle.

10. The method of claim 1 , including disabling the primary side switching signals according to the second selected output of the comparison when a converter switching cycle is complete.

11. The method of claim 10 , wherein the primary side switching signals are disabled with a delay of less than one switching cycle.

12. The method of claim 1 , wherein enabling and disabling the primary side switching signals turns the converter on and off, respectively, with zero current transitions, and maintains zero voltage switching or zero current switching while the converter is on.

13. The method of claim 1 , including controlling two or more phases of resonant converters.

14. A controller for a resonant power converter, comprising: a comparator that compares an output voltage or current of the converter to at least one reference voltage or current and generates results based on the comparison; and a circuit that operates one or more primary side switches of the resonant power converter by: enabling primary side switching signals based on a first selected result of the comparison; and disabling primary side switching signals based on a second selected result of the comparison; wherein a primary side switching signal for each primary side switch includes at least one off-on-off transition; wherein the operating one or more primary side switches of the resonant power converter by enabling and disabling primary side switching signals regulates the output voltage or current.

15. The controller of claim 14 , wherein the primary side switching signals for a pair of primary side switches are edge-synchronous, opposite polarity, and have 50% duty cycle.

16. The controller of claim 14 , wherein the circuit derives a frequency of the primary side switching signals from a clock frequency.

17. The controller of claim 16 , wherein an on period of the primary side switching signals is an integer multiple of a clock period and is synchronized with the clock frequency.

18. The controller of claim 16 , including a counter that derives the switching frequency from the clock frequency.

19. The controller of claim 14 , wherein two or more phases of resonant converters are controlled.

20. A resonant converter, including: a resonant power converter circuit; and the controller of claim 14 electrically connected to the resonant power converter circuit.